The invention relates to a compact low-pressure discharge lamp comprising a discharge vessel with electrodes and power supply leads, a discharge vessel mount on which the discharge vessel is mounted, and a cap, which comprises a housing, connecting contacts and a mounting plate with a ballast apparatus, with the mounting plate being fitted with the ballast arrangement in the interior of the cap housing, and having connections for electrical connection of the mounting plate to the power supply leads and to the connecting contacts.
Compact low-pressure discharge lamps such as these may also be provided with a reflector or an enveloping bulb. For relatively high wattages, the discharge vessel in this case comprises a tube which is composed of one or more pieces and is bent a number of times, and which is held in the housing with the aid of a mount part, whose shape is complex and which is composed of plastic or metal. One example of this is described in U.S. Pat. No. 4,456,854.
The mount part, whose shape is complex, for the discharge vessel leads firstly to correspondingly large dimensions for the low-pressure discharge lamp and secondly necessitates manual assembly of the lamp. The production costs for such compact low-pressure discharge lamps are thus relatively high.
The object of the invention is to provide a compact low-pressure discharge lamp of the type mentioned initially, which has a compact structure and can be produced easily, and hence cost-effectively.
In the case of the compact low-pressure discharge lamp according to the invention, the object is achieved by a mount for the discharge vessel having an essentially H-shaped cross section, with the mount comprising a plate with collars which run on the edge of each side of the plate. A cover part on the one hand and the housing of the cap on the other hand are now mounted on this discharge vessel mount.
The cover part may be in the form of an enveloping bulb or a reflector for the discharge vessel. If the compact discharge lamp is to be configured without an enveloping bulb or reflector, this cover part may also be in the form of a closure cap for the cap housing.
In the case of a circular-cylindrical cap housing, the plate of the H-shaped discharge vessel mount is advantageously circular.
The mounting of the discharge vessel is simple if the plate of the discharge vessel mount has two apertures or depressions in the form of half shells for holding the ends of the discharge vessel. The ends can then be mounted on the plate either by means of a hot fusion method, as is described in WO 0,101,437, or in a conventional manner by means of cap cement or adhesive. In the second case, the plate advantageously has a holding edge, for holding the cap cement or adhesive, around the apertures or depressions in the form of half shells, in which case, where apertures are used, the holding edge is advantageously fitted on the side of the plate facing the cap and, where depressions in the form of half shells are used, it is fitted on the side of the plate facing the cover part.
The discharge vessel can also be mounted on the discharge vessel mount by means of a trough, into which a part of the discharge vessel, such as a bend, is inserted. This type of mounting may also additionally be worthwhile for fixing the two ends of the discharge vessel, especially when the discharge vessel is long and has a number of bends.
On the side facing the cap, the plate also preferably has holders for contacts for electrical connection of the power supply leads to the electrical connections of the ballast arrangement on the mounting plate. One example of corresponding contact-making is contained in U.S. Pat. No. 6,008,570, where a cost-effective electrical connection between the power supply leads of the discharge vessel and the connections of the ballast arrangement on the mounting plate is produced by means of spring elements, which are held in holders on the closure cap.
In order to hold the cover part in a simple manner on the H-shaped discharge vessel mount, the latter has an at least partially circumferential groove on the inner face of its casing surface, in which groove formed-out regions, in the form of hooks, of the collar (facing the cover part) on the plate engage.
In order to mount the cap on the H-shaped mount, the cap housing has an at least partially circumferential groove on the inner face of its casing surface, in which groove formed-out regions, likewise in the form of hooks, on the other collar (facing the cap housing) of the plate engage.
Each collar advantageously has between 2 and 8 formed-out regions in the form of hooks. The formed-out regions in the form of hooks in this case have a width of between 1 and 30 mm depending on the cap housing diameter andxe2x80x94with respect to the two collarsxe2x80x94are arranged laterally offset with respect to one another, so that the projections of the formed-out regions, in the form of hooks, do not overlap in a plane at right angles to the lamp axis.
One or more relatively broad slots are incorporated in the collars facing the cover part and/or the cap housing, into which slots corresponding mating pieces in the form of ribs on the cover part and/or cap housing engage, thus producing protection against twisting. This avoids forces acting on the formed-out regions, in the form of hooks, when torques act about the lamp axis, so that the formed-out regions need absorb only tensile forces. This avoids the formed-out regions, in the form of hooks, breaking off, and avoids the connection becoming undone.
The formed-out regions in the form of hooks on the two collars are furthermore subdivided into a number of segments by narrow slots which extend as far as the plate. This segmentation leads to a reduction in the joining force. The number and width of the these segments are matched to one another such that, making use of the protection against twisting described above, the strength values required in the relevant Standards are complied with, and the joining forces are in a range which can also easily be coped with for manual assembly.
In addition, apertures can be provided on the plate, for holding tools to engage in. This allows fully automated assembly of the mount plate, fitted with the discharge vessel, together with the cover part, which is in the form of an enveloping bulb, reflector or closure cap, and the cap.
The H-shaped mount is composed of plastic, with the material advantageously being transparent.
The cover part is preferably composed of plastic, in which case, if the cover part is in the form of an enveloping bulb, it may comprise a glass bulb with a plastic edge fitted to it.
The optional configuration of the cover part as an enveloping bulb, reflector or closure cap makes it easy in production to change from compact low-pressure discharge lamps without enveloping bulbs to the same lamp type with an enveloping bulb or reflector. The pure plug-in and latching connections allow the lamp to be assembled very much more easily and fully automatically.